The argument of Kant's Second Analogy provides only for causal connections between successive appearances, but, as Kant himself immediately notes, in many cases cause and effect are simultaneous. This essay examines Kant's solution to the resulting problem of simultaneous causation. I argue that there are, in fact, at least two distinct problems falling together under the rubric 'simultaneous causation', both reflecting significant features of paradigmatic causal-explanatory scenarios within Newtonian mechanics - a problem about the 'persisting simultaneity' of a continuous or sustaining cause with its effect, and a problem about the 'instantaneous simultaneity' of what Kant calls the causality of a cause with the onset of its effect. An exploration of the ingenious conceptual resources which Kant brings to bear on these problems turns out to yield interesting and important insights regarding his philosophy of mathematics as well.